The proposed research will focus on evaluating the relationship between central nervous system (CNS) dysfunction, causal in many forms of behavior disorders, and autonomic nervous system (ANS) activity. The research will evaluate the hypothesis that rhythmic heart rate patterns, such as respiratory-sinus arrhythmia, reflect neural influences. The proposed research deals with the development of measures sensitive to neural control of the heart and with the empirical validation and clinical application of these techniques. The specific objectives of the research are: (1) to develop and validate quantitative indices of vagal tone to the heart; (2) to identify fetal distress through non-invasive monitoring of heart rate patterns; (3) to identify CNS dysfunction in neonates through non-invasive monitoring of heart rate and respiration. In previous research supported by the Research Scientist Development Award, spectral analysis techniques have been developed which are successful in identifying and quantifying a component of heart rate variability which covaries with vagal tone (V). In preliminary research with neonates V was related to general CNS status. The proposed research is an attempt to evaluate the sensitivity of V as an index of known pathophysiological states in brain-damaged infants and during perinatal distress. The techniques developed in the proposed research may evolve into an assessment technique sensitive to subtle shifts in CNS state. The assessment technique may potentially be useful in identifying pathophysiological states.